Holley Carb and catch tank - again!

[PJM Stag]

Hi Gents Had a good run to the New Forest over the weekend and car ran well. Under my ownership it has covered about 3000 miles. I have one problem, after a spirited run I have oil blowing all around the bonnet area from the catch tank. The catch tank has no pcv fitted and is "open" to atmosphere via the slight gap around the hose.

The only changes I have made since I bought "Ginger" are to lower the position of the catch tank from above the old expansion bottle to level with the base of the bottle, fixed the oil leak from the catch tank sight glass and fitted a new felt seal to the dip stick. I have also added a phenolic spacer to aid hot starting.

Car runs great with plenty of pull, starts instantly from cold appears to burn no oil (no smoking), but does chuck it out into the catch tank where it then gets blown around presumably by the "crankcase gases".

Car has a Holley carb with the pcv connection blanked off and the cam cover fed directly to the catch tank.

Over 400 miles the oil level has dropped from the top mark on the dipstick to the lower mark.

Advice please on whether to:
1. Fit a pcv to the catch tank and connect to the holley carb
2. Raise the catch tank
3. Fit a return oil line from the catch tank to the cam cover
4. All of the above
5. Any alternatives

[Hettiherald]

Having gone through a similar exersize with my stag, i would say fit the valve to lower the crankcase pressure. Did this on mine and now have no problems. I even made a catch tank out of an aluminium water bottle for under £20 including the pcv valve. Its nice to have a positive result for a change image.jpg

[V Mad]

I dont know what you are referring to when you say expansion bottle as that is part of the cooling system not the breather.

Presumably you have the cam cover connected to the catch tank inlet and have not fitted anything to the outlet?. But if oil is blowing out of the catch tank your car must be generating an excessive amount of crancase exhaust gas. If that is the case you need to do get that investigated for engine wear.

[PJM Stag]

The catch tank was originally fitted above the expansion bottle. There is no pressure at all at idle and if there was that much wear I would have thought there would be some pressure regardless of the revs.

[V Mad]

The blowby gasses at idle are much less than when you start driving the car especially under load.

Some picures of the catch tank and plumbing might help us see if there is something else amiss.

[flying farmer]

You are actually burning quite a lot of oil to go from max to min in only 400 miles, and that combined with the fact that oil is blowing out of the catch tank rather suggests that your engine is getting rather tired.


If it is still running well the best thing is to get rid of the catch tank and extend the breather hose so it vents below the car, the oil will still be disappearing but you will not see the resulting mess all over your engine bay.


Neil

[SaskStag]

I tried as Neil has suggested and had the breather pipe down below the engine bay. Google down-draught pipes. Interesting reading.
That helped settle all the oil leaks and stopped pressurising the catch tank. Then I added a PCV valve because it wasn't very environmentally friendly to keep the down-draught pipe. There are a number of PCV valve types to try and the numbers have been given out in previous threads, but a Fram 237 (6 cylinder Camaro) has worked very well for my car. I didn't have to make it fit the catch tank because it fits nicely between hoses. I did try and make sure it sits as vertical position as possible; all the oil leaks are gone, and there is suction at the oil cap when there was none before.
Tanya

[PJM Stag]

Thanks Tanya, I am currently working through a process of elimination but will certainly give this a try.

Paul

[arriva1]

Hi Gents Had a good run to the New Forest over the weekend and car ran well. Under my ownership it has covered about 3000 miles. I have one problem, after a spirited run I have oil blowing all around the bonnet area from the catch tank. The catch tank has no pcv fitted and is "open" to atmosphere via the slight gap around the hose.

The only changes I have made since I bought "Ginger" are to lower the position of the catch tank from above the old expansion bottle to level with the base of the bottle, fixed the oil leak from the catch tank sight glass and fitted a new felt seal to the dip stick. I have also added a phenolic spacer to aid hot starting.

Car runs great with plenty of pull, starts instantly from cold appears to burn no oil (no smoking), but does chuck it out into the catch tank where it then gets blown around presumably by the "crankcase gases".

Car has a Holley carb with the pcv connection blanked off and the cam cover fed directly to the catch tank.

Over 400 miles the oil level has dropped from the top mark on the dipstick to the lower mark.

Advice please on whether to:
1. Fit a pcv to the catch tank and connect to the holley carb
2. Raise the catch tank
3. Fit a return oil line from the catch tank to the cam cover
4. All of the above
5. Any alternatives

image.jpg


Had similar issue with weber but after fitting PCV , see bulkhead in photo, runs brilliantly and no oil issues
Trev

[PJM Stag]

[ATTACH=CONFIG]30288[/ATTACH]


Had similar issue with weber but after fitting PCV , see bulkhead in photo, runs brilliantly and no oil issues
Trev

That's encouraging, I dont want to have to do a rebuild unless absolutely necessary.

Thanks

Paul

[mike@thenook]

Hi Paul,

it does sound as though you are burning more oil than is right as Neil says but try re-plumbing first - have a look at my post in the technical section and photos in my album.

Cheers

Mike

[PJM Stag]

Thanks Mike had a PM pointing me in the right direction and I am now blatantly copying your set up. New catch tank arrived today so now patiently waiting for the pcv to turn up.

The car is not so much burning the oil just pumping it into the catch tank. If I could rig up a return line to the sump it would solve my problem perhaps I should just feed it back into the oil filler.

The gauze breather in the cam cover is now clear and ready to go back onto the car.

[mike@thenook]

Feel free to copy, its what its there for - You'll probably find the PCV will stop the oil being pulled through, or that is what it is intended to do. At low revs/idle it alllows free flow but at high revs it shuts off preventing any draw through of gases or oil.
Got to say mine works perfectly now, no oil leaks at all and the only thing I get in the CT is some oily vapour, not much though.
It will pull from 750 rpm in o/d top gear now, never had that ability with my old Strom's.

Cheers